STATE AGRICULTURAL SOCIETY. 119 



an inch deep over the surface of the soil. In Belgium and on the 

 Rhine, it is found that the grape matures best when the soil is 

 covered with fragments of black clay slate. Girardin found in a 

 series of experiments on the cultivation of potatoes, that the 

 time of their ripening varied eight to fourteen days according to 

 the color of the soil. He found on August 25th, in a very dark 

 humus soil, twenty-six varieties ripe; in sandy soil twenty; in 

 clay nineteen; and in white lime soil, only sixteen. It is not 

 difficult to assign other causes that will account in part for the 

 results here mentioned ; there seem to be no accurate and exten- 

 sive observations on this point. That dark soils may actually 

 attain an increased temperature of three to eight degrees over 

 light colored soils, is a matter of direct observation. 



2. Rapidity with which the soil cools and warms. — Schiibler found 

 that different soils heated to the same point required different 

 times to cool down through a given number of degrees. In the 

 following table are given his results, lime sand being assumed as 

 100. 



Lime sand, _ 100 



Slate marl, ._ _ 98.1 



Quartz sand, 95.6 



Potters' clay,.. 76.9 



Gypsum, 73.8 



Clay loam, 71.8 



Plough clay land, 70.1 



Heavy clay, 68.4 



Pure gray clay, 66.7 



Garden earth, 64.8 



Fine carb. lime, 61.3 



Humus, _ 49.0 



Magnesia, _ 38.0 



It is seen that the sandy soils cool most slowly, tlien follow 

 clays and heavy soils, and lastly comes humus. It must be 

 remembered that the exi)erimeiits were instituted on dry soils, 

 i. e. artificially deprived of water, and hence do not api)ly to the 

 soil in its natural state, in wliicli water is rarely absent. 



As to the rapidity with which various soils become warmed by 

 the heat of the sun or of the day, no observations of any agri- 

 cultural value have been instituted to my knowledge. It is easy 



